Process of making cubic texture silicon-iron



April 1954 D. M. KOHLER ETAL 3,130,092

PROCESS OF MAKING CUBIC TEXTURE SILICON-IRON 3 Sheets-Sheet 1 Filed May29, 1959 ATTORNEYS.

April 21, 1964 M KOHLER AL 3,130,092

PROCESS OF MAKING CUBIC TEXTURE SILICON-{RON Filed May 29, 1959 3Sheets-Sheet 2 E 9 k a Z 270 kg- INVENTORJ. 1.28mi; J44! M/(orase [1Y0BYWVM April 1964 D. M. KOHLER ETAL 3,130,092

PROCESS OF MAKING CUBIC TEXTURE SILICON-IRON 3 Sheets-Sheet 3 Filed May29, 1959 IT'TORNYS- United States Patent Ofi ice 3,130,092 Patented Apr.21, 1964 3,130,092 PROCESS OF MAKING CUBIC TEXTURE SILICON-IRON Dale M.Kohler, Middletown, and Martin F. Littmann,

West Middletown, Ohio, assignors to Armco Steel Corporation, Middletown,Ohio, a corporation of Ohio Filed May 29, 1959, Ser. No. 816,889 9Claims. (Cl. 148-111) This is a continuation-in-part of the inventorscopending application of the same title, Serial No. 687,988, filedOctober 3, 1957, now abandoned.

Silicon-iron sheet stock having a high degree of preferred orientationhas come into widespread commercial use, and in many fields the highlydirectional permeability of such stock has brought about radical changesin the design of transformers and other electrical apparatus. Suchsilicon-iron products have had a crystal orientation which may bedesignated as (110) [001] in the standard notation of Millers indices.This orientation means that the product has a high permeability in therolling or straight-grain direction, but a poor permeability in otherdirections.

The crystalline structure of silicon-iron is cubic, so that theindividual crystals in a polycrystalline material may be visualized as aseries of cubes. In the orientation mentioned above, a cube edge [001]is parallel to the rolling direction and a dodecahedral face (110) isparallel to the rolling plane. Four of the cube edges are parallel tothe direction of rolling, but no face of the cube is parallel to thesurfaces of the sheet. Thus, the orientation has been referred to as acube-on-edge type. The cube edges which lie transverse to the directionof rolling are not parallel to the surfaces of the sheet. Consequently,the transverse permeability is low because the most effective path forthe magnetic flux, is parallel to the cube edges.

It has been realized that if it were possible to so orient the crystalsthat while a cube edge remained parallel to the rolling direction,another cube edge would lie perpendicular to the rolling direction andin the plane of the sheet surface, a material would be obtained Whichnot only would have a high straight grain permeability but would alsohave a high transverse or cross grain permeability. Such a product wouldhave many additional uses, particularly in the construction oftransformers having cores made from E or I-shaped laminations and inrotating electrical machinery. The orientation just described is a (100)[001] orientation by Millers indices and for convenience hereinafterwill be referred to by the arbitrary expression cubic texture.

Hitherto it has not been possible to attain a cubic texture withcommercial reproducibility and at commercial cost by starting with apolycrystalline silicon-iron and orienting the crystals therein by acombination of cold reductions and heat treatments. It is a primaryobject of this invention to provide such a process.

It is an object of the invention to provide an oriented product ofpolycrystalline character having more than one direction of highpermeability.

It has been noted that as silicon-iron having the cubeon-edge type oforientation becomes thinner, the hysteresis loss of the materialincreases sharply, probably because of the increased efiect of theunfavorable crystallographic directions which lie in the plane of thesheet. It is an object of this invention to provide a polycrystallinesilicon-iron which minimizes this defect.

The attaining of a high degree of cubic texture in silicon-iron isaccomplished by secondary recrystallization of a material characterizedby some grains which are already in the desired orientation (or within acomparatively few degrees of it), which grains or nuclei grow during thesecondary recrystallization at the expense of grains having asubstantially different orientation.

It is an object of this invention to provide a method of making amaterial, and a material so made, which can be depended upon to have acomparatively large number of nuclei in or near the [001] orientationand a minimal number of grains in other orientations which might alsotend to grow during secondary recrystallization at the expense of grainshaving substantially different orientations.

These and other objects of the invention which will be set forthhereinafter or will be apparent to one skilled in the art upon readingthese specifications are accomplished in that procedure and product ofwhich an exemplary embodiment will hereinafter be described. Referenceis made to the accompanying drawings wherein:

FIG. 1 is a stereogram of the cube poles of representative individualgrains of a silicon-iron piece characterized by the cube-on-edge type oforientation.

FIG. 2 is a diagrammatic representation of this type of orientation.

FIG. 3 is an X-ray pole-density stereogram of (200) poles showing aderivative orientation designatable as (111)[1l2], produced by coldrolling the material of FIG. 1.

FIG. 4 is a diagram of this type of orientation.

FIG. 5 is an X-ray pole-density stereogram of (200) poles showing aderivative orientation which may be designated as ()[0O1], resultingfrom the recrystallization of the product of FIG. 3.

FIG. 6 is a diagram of this type of orientation.

FIG. 7 is an X-ray pole-density stereogram of (200) poles of materialshowing a derivative orientation (hereinafter described) produced byanother stage of cold rollmg.

FIG. 8 is a diagram of this orientation.

FIG. 9 is an X-ray pole-density stereogram of (200) poles of thematerial of FIG. 7 after a primary recrystallization.

FIG. 10 is a stereogram of the cube poles of individual grains of thematerial of FIG. 9 after having been subjected to secondaryrecrystallization, and showing cubic texture, designatable as (100)[001].

FIG. 11 is a diagram of this orientation.

On the X-ray pole-density stereograms, FIGS. 3, 5, 7 and 9, numericalindications of the intensities are shown in times random.

The silicon-iron material employed in the practice of the inventionshould have a silicon content sufiiciently high to prevent phase changesduring heat treatment, but low enough to prevent brittleness duringrolling. A range of 2.5 to 4.0% silicon is satisfactory. The finalproduct should have a high degree of purity by which is meant freedomfrom carbon, sulphur, nitrogen, oxygen, inclusions and the like. Purityis usually attained in the production of the metal in known ways,although carbon may be reduced at any early heat treating stage of therouting by subjecting the material to a decarburizing anneal, preferablyin accordance with the teachings of the Carpenter et a1. Patent No.2,287,467, issued June 23, 1942.

By way of example, a preferred range of silicon is from 2.90 to 3.30%.The cube-on-edge material should contain .007% or less carbon, .03 to.15 manganese, and .015 to .030% sulfur, the remainder beingsubstantially all iron with normal impurities, and with a total oxidecontent of .015 or less.

The low carbon content is important because it makes for low core lossvalues. The total oxide content is preferably no more than .004% in thefinal product just before secondary recrystallization.

Hot rolled silicon-iron is generally characterized by an incompletelydeveloped preferred crystal orientation. In both hot and cold rolling,the crystals not only become longer but tend to change their orientationby a process of slip in preferred directions and on preferredcrystallographic planes. In this manner, deformation produces apreferred texture in the material, with the individual crystals invarious conditions of stress. Raising the temperature after deformationpermits the crystals to release their stresses throughrecrystallization; and the crystals generally change-in orientation bythe adoption of adjacent positions of lower energy.

The art has hitherto learned various procedures for producing frompolycrystalline silicon-iron the material above designated as of thecube-on-edge type, by subjecting the hot rolled material to one or to aseries of controlled cold reductions followed by heat treatments. Ourresearches have indicated that the cube-on-edge or (110) [001]orientation is in many instances at least a derivative of a (111) [112]orientation produced by tilting the crystals in the rolling direction bya sufficient amount and then causing them to assume a related low energyposition which is the cube-on-edge orientation. As examples of suitableprocedures, reference may be made to Patent 2,158,065, dated May 16,1939, in the names of Cole et al., Patent 2,287,466, dated June 23,1942, in the name of Carpenten'Patent 2,307,391, dated January 5, 1943,in the names of Cole et al., and Patent 2,599,340, dated June 3, 1952,in the names of Littmann et al. FIG. 1 of this application is astereogram of the cube poles of typical cube-on-edge silicon-iron,clearly indicated in a crystal position such as is illustrated in FIG. 2hereof. In this figure two small cubes 1 and 2 have been shown, therolling direction being indicated by an arrow, and the planes of thesurfaces of the sheet material being understood to be parallel to theplane of the paper on which the drawing is made.

It has now been discovered that it is possible to take commercialpolycrystalline silicon-iron having the (100)- [001] orientation andconvert it to a polycrystalline material having the (100) [001]orientation or cubic texture by a series of progressive steps. Materialsuitable for this process consists of sheet or strip of any thicknesshaving a cube-on-edge orientation as illustrated in FIGS. 1 and 2,prepared in any suitable way including the procedures of the abovementioned patents.

It will be understood that the commercial starting material will havepurity within the limits set forth above, will have been decarburized tothe desired degree, and will have been subjected to a final heattreatment at high temperature (generally around 2200 F.).

The first step is to cold reduce such material within certain limits soas to bring about the tilted condition of the crystals indicated in thepole-density stereogram which forms FIG. 3 hereof and illustrated by thesmall cubes 3 and 4 of FIG. 4. A cold reduction generally of about 55%to 90% will produce the eifect, it being understood that the tiltingwill vary with the degree of cold rolling reduction. The orientation atthis stage will respond generally to the notation (111) [112] of Millersindices.

It has been found that the optimum ranges for cold rolling in the firststage just described difier depending upon whether the immediate annealwhich follows is an open anneal or a box anneal. If the anneal is anopen anneal, best results will be obtained if the reduction is about 75%to 87%. If a box anneal is used at this point, best results will beattained at reductions of about 60% to 85%.

each way about the rolling direction from the rolling plane. While somevariation in this texture can be tolerated, it is preferable to have thecrystals preponderantly with their (120) planes in substantial parallelism with the planes of the sheet material.

The intermediate anneal which accomplishes this is an anneal, eitheropen or box, preferably at about 1200 to 2200 F and preferably in dryhydrogen. If an open or strip anneal is used, a temperature of 1500 to1700 F. is preferred. If a box anneal is used, a preferred range is 1400to 1600 F., although good results may be obtained over the entire rangegiven above, namely 1200 to 2200 F. The annealing atmosphere should besuch as to preclude undue oxidation.

The material is next subjected to a second cold rolling treatment. Inthe cold reduction the crystals are again tilted, and this produces thecomplex pole density stereogram which forms FIG. 7 hereof. A study ofthis stereoa gram will indicate that the orientation of the crystals issubstantially that diagrammed at 7, 8, 9 and 10 in FIG. 8. The crystalorientation illustrated is obtained by rotating the cubes substantially30 each way about the transverse axis, and then substantially 10 aboutan axis normal to the sheet surface. If this index were to be describedby the use of Millers indices, It would approximate a (7,10,15 [E310]orientation.

Again to produce this orientation the cold rolling treatment must becontrolled as to extent. A cold rolling reduction of about 50% to 80%Will generally be found effective. This second cold rolling is, however,affected by the nature of the intermediate anneal previously outlined.Thus if the intermediate anneal is an open or strip anneal an optimumrange of reduction in the second The material is next subjected to anintermediate ancold rolling treatment will be found to be about 60% to70%. If a box anneal has been practiced, a percentage reduction in thesecond stage of cold rolling of a some what higher value, namely 70% towill be found best.

A material oriented as shown in FIGS. 7 and 8 can be caused to assumethe orientation indicated by the pole density stereogram set forth hereas FIG. 9, by primary recrystallization. An examination of thisstereogram will indicate that while the cube edges have been realignedin the rolling direction with reasonable uniformity, the tilting of thecube faces with reference to the plane of the sheet stock has broadenedand becomes more heterogeneous. A large number of the grains are tiltedby more than 22 /2 from the position illustrated in FIG. 6 as the 120)[001] orientation, and a substantial number have been tilted into the[001] position or within a few degrees of it. It is these last mentionedgrains which form the nuclei for the subsequent conversion of the stockto one having preponderantly the cubic orientation, in the process ofsecondary recrystallization.

The skilled worker in the art will understand that primaryrecrystallization occurs rapidly at a relatively lower temperature, inthe range of say 1075 to 1900" R, while secondary recrystallizationrequires time at a higher temperature of about 1900 to 2300 F., with apreferred temperature at about 2200 F. Consequently after the last coldrolling treatment, the primary and secondary recrystallizataions areusually carried on in a single heat treatment under conditionshereinafter to be specified.

As in other procedures for the production of highly orientedsilicon-irons involving a series of cold reductions which are criticalas to amount, it will be necessary to calculate back from the finishedgauge in order to determine the proper thickness of the startingmaterial. Beyond this there is no limit on the present invention eitheras to the thickness of the final product or as to the thickness of thestarting material.

The original material is, of course, an ingot of silicon-,

iron alloy which may be processed into suitable cube-onedge sheet orstrip material in a variety of ways as has been described heretofore.The cube-on-edge stock which forms the starting material here shouldhave a high degree of perfection of the (110) [001] orientation. Theterm high degree should be taken as indicating that the material is sooriented as to have a straight grain permeability of at least about 1700at H= oersteds, and preferably higher. The cube-on-edge materialpreferably has a relatively large grain size (about 5 mm. in diameter).

in the next stage of the process, the material having the high degree of(110) [001] orientation is cold re.- duced to a thickness of about /2 toits original thickness, i.e., with a reduction of 55% to 90%, or withinthe narrower preferred ranges discussed above. It is thenrecrystallized. Varying heat treatments at this point are possible. Anopen, strand or continuous anneal may be used; but a box anneal in aninert or reducing atmosphere such as hydrogen is preferred. The materialmay be heated to a temperature of about 1200 to 2200 F. and held forabout two hours at such temperature. Assuming the product has thedesired purity and has previously been decarburized to, say, .01% orlower, the essentials here are to efiect a primary recrystallization andfit the material for further cold reduction, while avoiding thedevelopment of oxides at its surfaces.

Next the product having the high degree of (120) [001] orientation isagain cold reduced to about /2 to its thickness or with a reduction of50% to 80%, or preferably within the narrower preferred ranges discussedabove.

The final rolled product is then given a box anneal in hydrogen. Whilethe attainment of a recrystallizing temperature will produce asubstantial number of grains having the desired (100) [001] orientationif the preceding steps have been performed, a product in which at leastthe majority of the grains have the (100) [001] orientation is obtainedwhen discontinuous or selective grain growth takes place. This graingrowth, sometimes called secondary recrystallization, takes place attemperatures above about 1900 F. To promote secondary grain growth theannealing atmosphere should be pure and non-reactive. Annealingseparators may be used. While hydrogen is suitable, the use of vacuum orinert atmospheres like helium, argon or the like is desirable. In thesecondary recrystallization, the (100) [001] crystals tend to grow atthe expense of the other crystals, producing a very nearly perfectorientation in the cubic texture.

The final heat treatment is preferably carried on in accordance with theteachings of the copending application of Kohler (one of the inventorsherein) entitled The Production of Oriented Silicon-Iron Sheets bySecondary Recrystallization, Serial No. 813,289, filed May 14, 1959,which teaches in essence the use of an atmosphere in the final heattreatment of hydrogen or a non-reactive gas such as argon or helium,which atmosphere contains a very small amount of a highly polar compoundsuch as hydrogen sulphide, sulphur dioxide, an oxide of carbon, or amixture of these. The highly polar compound is believed to be absorbedor adsorbed on the crystal planes at the surfaces of the sheet stock soas to satisfy the positive unsatisfied charges there, the result being ashifting of the energies of crystals of difiering orientations in such away that the (100) [001] orientation becomes the lowest energyorientation by a substantial amount, making for a more positive andcomplete cubic texture orientation in the stock.

The final anneal maybe and preferably is a box anneal, although it hasbeen found that an open, strand or continuous anneal may be used.

The result of the final anneal is illustrated by the stereogram FIG. 10,and diagrammed in FIG. 11. It has been found readily possible inaccordance with the teachings of this application to make a silicon-ironprodnct in which in excess of 90% of the surface area of the sheet stockis occupied by grains having the cubic texture, the grains neverthelessbeing comparatively small, which is favorable to core losscharacteristics. A grain size of 7 (ASTM) at 1x magnification or smallercan be produced especially if box annealing treatments are employed.

Example A coil of silicon-iron .014 inch in thickness, containing 3%silicon, and already having the (ll0) [001] orientation was selected.This material had a permeability at H =10 of about 1820 in the straightgrain direction, and the orientation shown in FIG. 1. It had a grainsize of about 7 in accordance with the ASTM standards at 1Xmagnification, after hydrogen annealing for 24 hours at 2200 F. Thiscoil was pickled and cold reduced to .0038 inch and exhibited theorientation shown in FIG. 3. The strip was then strand annealed inhydrogen for 2 minutes at 1600 It now had the (120) [001] texture shownin FIG. 5.

The material was then again cold rolled to a thickness of .0018 inch.Its orientation at this stage is shown in FIG. 7.

Finally, the material after shearing into Epstein samples (3 cm. X 30.5cm.), samples being taken both in the rolling direction and transverseit, was given an anneal in hydrogen, the heating cycle being such thatit took the material about 8 hours to attain a temperature of 2200 F. Itwas held at this temperature for about 5 hours.

Examination of the surface of the final product indicated that at leastabout of its area was occupied by crystals which were the product ofsecondary crystal growth. FIG. 10 is the X-ray pole figure of theproduct. The product tested as follows:

Permeability at H=10 oersteds, 1840 (straight grain) Permeability atH=10 oersteds, 1780 (cross grain) Modifications may be made in theinvention without departing from the spirit of it. The invention havingbeen described in an exemplary embodiment, what is claimed as new anddesired to be secured by Letters Patent is:

1. A process of producing silicon-iron for magnetic uses having highstraight-grain and high cross-grain permeabilities, which comprisesproviding a polycrystalline ferrous sheet stock containing substantially2.5 to 4.0% silicon and having preponderantly a [001] crystalorientation by Millers indices, cold rolling said siliconiron with areduction of substantially 55 to 90%, and subjecting said silicon-ironto a primary recrystallization in a heat treatment at about 1200 F. to2200 F., then again cold rolling said silicon-iron with a reduction ofsubstantially 50% to 80%, and heat treating the siliconiron at atemperature of 1900 to 2300 F. under conditions productive of secondaryrecrystallization whereby first to subject said silicon-iron to primaryrecrystallization, and thereafter to secondary recrystallization toconvert said silicon-iron to a polycrystalline product havingpreponderantly a (100)[001] orientation.

2. A process of producing silicon-iron for magnetic uses having highstraight-grain and high cross-grain permeabilities, which comprisesproviding a polycrystalline silicon-iron containing substantially 2.5 to4.0% silicon having preponderantly a ()[001] crystal orientation byMillers indices, cold rolling said siliconiron with a reduction ofsubstantially 55 to 90%, whereby to convert it to a material having a(111) [112] orientation, subjecting said silicon-iron to a heattreatment at above the recrystallization temperature whereby to convertthe orientation to [0011, again cold rolling said siliconiron with areduction of substantially 50 to 80% to convert the last mentionedorientation to a derivative orientation in which the crystals are tiltedin both transverse directions as respects the rolling direction, andsubjecting said silicon-iron to a heat treatment at about 1900 to 2300F. under conditions productive of sec- 7 ondary recrystallization;whereby I to effect a primary recrystallization followed by a secondaryrecrystallization.

3. The process claimed in claim 2 wherein the starting material has astraight-grain permeability of at least about 1700 at H 10.

4. A process of producing silicon-iron sheet stock for magnetic useshaving high straight-grain and high crossgrain permeabilities, whichcomprises hot rolling an ingot of silicon-iron containing substantially2.5 to 4.0% silicon, converting it by at least one cold rollingtreatment followed by a recrystallization to a (110) [001] orientationwith a straight-grain permeability of at least about 1700 at amagnetizing force of oersteds, converting it by an additional coldrolling treatment with substantially 55 to 90% reduction and a primaryrecrystallizing heat treatment through a (111) [112] orientation topreponderantly a (120) [001] orientation, and converting it by a coldrolling reduction of substantially to 80% and a primary recrystallizingheat treatment through a derivative cold rolled orientation in which the(120) [001] crystals are tilted in both transverse directions asrespects the rolling direction, .to an orientationin which the cubeedges are generally aligned in the rolling direction but the cube facesare tilted away from the 110) position, the said tilting being such thata substantial number of the grains have their cube faces substantiallyparallel to the faces of the sheet stock, and then subjecting the stockto a secondary recrystallization to cause said last mentioned grainsrtogrow, until the greater part ofthe face area of said sheet stock isoccupied by grains having a (100) [001] orientation.

5. The process claimed in claim 4 in which the said final heat treatmentcarries the said silicon-iron to a temperature of at least substantially2000 F. and includes a soaking at the said temperature, whereby saidsecondary recrystallization is caused to take place.

6. A process of making cubic texture silicon-iron sheet stock containingsubstantially 2.5% to 4.0% silicon which comprises providing asilicon-iron sheet stock the grains of which are characterized by a(110) [001] orientation, cold rolling said stock with a reduction ofsubstantially to 90% reduction, annealing said stock at a temperature ofsubstantially 1200 to 2200 F., again cold rolling said stock with areduction of substantially 50% to 80%, subjecting said stock to' aprimary re crystallization at a temperature of substantially 1075 to1900 F., and then to a secondary recrystallization at a temperature ofsubstantially 1900 to 2300 F.'

7. The process claimed in claim 6 in which said secondaryrecrystallization is carried on in a non-oxidizing atmosphere containinga minute quantity of polar compound chosen from a class consisting ofoxides of sulfur and carbon and hydrogen sulfide.

8. A process of making cubic texture silicon-iron sheet stock containingsubstantially 2.5% to 4.0% silicon, which comprises providing asilicon-iron sheet stock the grains of which are characterized by a(110) [001] orientation, cold rolling said stock with a reduction ofsubstantially 75% to 87%, strip-annealing said stock at a temperature ofsubstantially 1500 to 1700 F., again cold rolling said stock with areduction of substantially to subjecting said stock to a primaryrecrystallization at a temperature of substantially 1400 to 1700" F.,and to a secondary recrystallization at a temperature of substantially190 to 2300 F.

9. A process of making cubic texture silicon-iron sheet stock containingsubstantially 2.5 to 4.0% silicon, which comprises providing asilicon-iron sheet stock the grains of which are characterized by a(110) [001] orientation, cold rolling said stock with a reduction ofsubstantially 60% to 85%, box annealing said stock at a temperature ofsubstantially 1400 to 1600 F., again coldrrolling with a reduction of70% to and then subjecting said stock to a primary recrystallization anda secondary recrystallization in a box anneal at a temperature ofsubstantially 1900 to 2300 F.

References Cited in the file of this patent UNITED STATES PATENTS2,473,156 Littmann June 14, 1949 2,867,558 May Jan. 6, 1959 2,992,951Aspden July 18, 1961 2,992,952 Assmus et a1. July 18, 1961 FOREIGNPATENTS 1,009,214 Germany May 29, 1957 UNITED STATES PATENT OFFICE(l-ERTIFICATE OF CORRECTION Patent No, 3,130,092 April 21 1964 Dale M.Kohler et a1,

It is hereby certified that error appears in the above numbered patentreq'iiring correction and that the said Letters Patent should read ascorrected below.

Column 3, line 38 and column 6, line 46 for "(100 each occurrence, read(110) column 4, line 26 for "10" read 10 Signed and sealed this 8th dayof September 1964,

(SEAL) Attest:

ERNES'IW. SWIDER EDWARD J. BRENNER Aitesting Officer Commissioner ofPatents

1. A PROCESS OF PRODUCING SILICON-IRON FOR MAGNETIC USES HAVING HIGHSTRAIGHT-GRAIN AND HIGH CROSS-GRAIN PERMEABILITIES, WHICH COMPRISESPROVIDING A POLYCRYSTALLINE FERROUS SHEET STOCK CONTAINING SUBSTANTIALLY2.5 TO 4.0% SILICON AND HAVING PREPONDERANTLY A (100)(001) CRYSTALORIENTATION BY MILLER''S INDICES, COLD ROLLING SAID SILICONIRON WITH AREDUCTION OF SUBSTANTIALLY 55 TO 90%, AND SUBJECTING SAID SILICON-IRONTO A PRIMARY RECRYSTALLIZATION IN A HEAT TREATMENT AT ABOUT 1200*F. TO2200*F., THEN AGAIN COLD ROLLING SAID SILICON-IRON WITH A REDUCTION OFSUBSTANTIALLY 50% TO 80%, AND HEAT TREATING THE SILICONIRON AT ATEMPERATURE OF 1900* TO 2300*F. UNDER CONDITIONS PRODUCTIVE OF SECONDARYRECRYSTALLIZATION WHEREBY FIRST TO SUBJECT SAID SILICON-IRON TO PRIMARYRECRYSTALLIZATION, AND THEREAFTER TO SECONDARY RECRYSTALLIZATION TOCONVERT SAID SILICON-IRON TO A POLYCRYSTALLINE PRODUCT HAVINGPREPONDERANTLY A (100)(001) ORIENTATION.